Ethylbenzene (EB) is used predominantly for the production of styrene monomer obtained through dehydrogenation. Presently much of the EB being produced is obtained by alkylation of benzene (Bz) with ethylene (Eth) under a variety of alkylation conditions. One type of alkylation process which is conventional is to employ relatively high pressures and temperatures to obtain vapor phase reaction conditions wherein the ethylene and benzene are converted in the presence of catalytic materials. Both single and multiple catalyst bed processes are well known in the art.
For example, U.S. Pat. No. 4,400,570 to Butler et al, discloses a process for manufacturing ethylbenzene for use in styrene wherein ethylene and benzene are reacted with stream over a TEA-silicate catalyst. One problem in the production of EB by such methods is the production of unwanted by-products which can be very detrimental because some of the by-products may be very difficult, or impossible, to separate from the desired EB product. Thus, as an example, the production of xylene in these types of processes is very undesirable since separation of xylene from the EB product is very difficult from a processing standpoint. In addition to the requirement that the catalyst employed in such processes be selective to the desired EB product it is also desirable to obtain acceptable conversion of the reactants to alkylated products. The ability of different catalyst materials to convert the raw feed materials into products is sometimes referred to as its "activity". "Conversion" is normally measured as a percentage of the amount of feed materials which will be converted into products during the reaction. The ability of the catalyst to maintain high conversion rates (i.e. retain activity) is very important.
Deactivation of catalysts is one major problem in catalytic alkylation processes since, even if high conversion rates are obtained initially, the failure to maintain good conversion over a long period of time requires expensive catalyst changeouts and/or regeneration procedures.
Another critical area in the formation and production of EB is in the feed/product ratio. Any factors which can significantly lower the feed/product ratios without degrading activity or conversion, and without increasing xylene production, is very desirable.
Thus it would be desirable to obtain a process in which conversion of reactants to EB can be obtained without production of unwanted xylene by-products and without the necessity of frequently regenerating or replacing the catalytic material employed.